Building block



FIG. 1 is a front-top perspective view of a building block showing my new design;

FIG. 2 is a front-bottom perspective view thereof;

FIG. 3 is a rear-top perspective view thereof;

FIG. 4 is a rear-bottom perspective view thereof;

FIG. 5 is a front elevational view thereof;

FIG. 6 is a rear elevational view thereof;

FIG. 7 is a left elevational view thereof;

FIG. 8 is a right elevational view thereof;

FIG. 9 is a top plan view thereof; and,

FIG. 10 is a bottom plan view thereof. 

CLAIM The ornamental design for a building block, as shown and described. 